The use of dental prostheses to replace missing or damaged teeth is commonplace. Typically, artificial roots, or implants, are implanted into the bone of the patient's jaw and are used to provide structural support to an intermediate abutment. One or more artificial replacement teeth or crowns are then fastened to the abutment typically by cements or screws.
FIGS. 1A to 1D illustrate partial cross-sectional side views of one example for implanting a typical crown within the mouth of a patient. Depending upon the number of teeth to be replaced, one or more holes may be bored within the bone of the jaw. As shown in FIG. 1A, a portion of the gums or gingiva 14 may be cut open to expose the underlying bone 10, e.g., maxilla or mandible, into which a drill bit 16 may be used to bore open a hole 12. An anchoring dental implant 18, optionally threaded, may be implanted within hole 12 and covered by gingival 14 to allow for healing and for the implant 18 to take hold within bone 10, as shown in FIG. 1B.
Once the implant 18 has been desirably positioned within bone 10, an abutment assembly 20 may be securely attached to implant 18, e.g., by a threaded pin 22 coupling to an implant receiving well 26 defined within implant 18 such that abutment 24, which defines a portion projecting through gingival 14 from implant 18 once coupled to implant 18, as shown in FIG. 1C. With abutment 24 secured to implant 18, crown 28 which defines crown opening 30 may be secured upon abutment 24 by utilizing a number of securement mechanisms, such as cement or a fastener such as a screw. Other securement mechanisms have also included interference fitting such as with a cross-bar or O-ring type attachment, magnets, etc.
Because the implants, abutments, and crowns are subjected to high compressive and shear forces, initial positioning of the crowns is important not only to provide adequate structural support but also to ensure patient comfort. However, while utilizing cement to attach the crown to the abutment initially allows for aligning the crown more naturally with the dentition of the patient, the tolerance for mistakes is low once the cement has set because of the difficulty and expense in removing a cemented crown from the abutment. Screw-type retention devices may also provide for good securement of the crown to the abutment, but occlusal contact within the patient dentition is often misaligned resulting in a variety of complications. For instance, misaligned crowns result in a compromised occlusal table which in turn may lead to chipping of the crowns as well as poor aesthetic appearance of the patient's dentition.
Previous devices have attempted to create removable denture retention devices, such as that disclosed in U.S. Pat. No. 5,516,288, which is incorporated herein by reference in its entirety. Such systems are described which implant a screw within the jawbone of the patient while utilizing an abutment structure coupled to the implant portion via a ball joint made of shape memory materials. A restorative crown or dental replacement member is then attached to the abutment via conventional retention methods. However, such a device fails to disclose the use of shape memory materials utilized in the interaction between the abutment and the crown or bridge itself, as described in further detail below, as such an interaction facilitates the retention and retrieval of the crown or bridge from the abutment and/or implant.
Accordingly, there exists a need for methods and devices which are efficacious in facilitating not only the retention of oral appliances or prostheses, such as crowns or bridges, along the dentition of a patient but also the removal and/or repositioning of the crown or bridge.